UTC stands for Coordinated Universal Time, which is accepted as an international standard and is used to regulate clocks around the world.
Before people started using UTC, Greenwich Mean Time was used. However, Greenwich Mean Time (GMT) introduced in 1847 quickly began to accumulate errors due to changes in the Earth's rotation speed. First universal time was adopted (in 1928), and then, in 1972, coordinated universal time was adopted. UTC is an abbreviation, but built nonlinearly. According to the most common version, the abbreviation CUT (Coordinated Universal Time) does not sound good enough, and may also be misinterpreted without context. Therefore, the letters in the abbreviation were rearranged and as a result the whole world knows the coordinated universal time under the acronym UTC.
An important feature of UTC is its lack of transition to summer or winter.
The first difference between UTC is a more accurate standard of time measurement. Greenwich Mean Time (GMT) is based on the average meridian solar day. Earth's rotation is gradually slowing, so the solar day is shifting. Because of these errors, Greenwich time has fallen out of use. UTC is based on the atomic time, which is independent of the rotation of the planet or the Sun. However, UTC is also an insufficiently accurate standard for calculating time: every year you need to add one second. This second is called “Second Coordination” and is usually added on June 30 or December 31.
This time standard allows more accurate timekeeping and to avoid errors. UTC also regulates time zones, of which there are only 24 on the planet. The Greenwich meridian (UTC 0) was traditionally taken as the reference point, negative UTC figures are to the left of it and positive ones are to the right. So, for example, Moscow is in the UTC+3 belt, and New York is in the UTC-5 belt (UTC-4 in summer). The introduction of a single, understandable system of time zones allowed us to avoid confusion when moving, flying and planning time. UTC belts are relatively uniform, but often pass along state borders. If the country is small, but “creeps” with its border on neighboring time zones, a uniform time format is introduced in its territory. There are 11 UTC time zones in Russia: from UTC+2 in Kaliningrad to UTC+12 in Kamchatka.